Army officer Janelle Tham had to fight a battle of a different sort when her six-year-old son Keon Teh came down with dengue in April last year.

It was one that the 34-year-old had to face without her husband, also an army officer, who was abroad on a training stint at the time.

She had to juggle her work with taking care of Keon as well as her younger son, four-year-old Kyler, who also fell ill around the same time.

She began getting worried when Keon started running a high fever, which hit as high as 40 deg C and persisted over three days.

At the time, they had been living in a cluster house - one of a group of three-storey terrace houses with shared facilities such as a garden - in Ang Mo Kio, and she had heard of a few cases of dengue among their neighbours.

She took leave from work to take care of her sick child, but still had to attend to some calls to hand over her work on her first day of leave.

She said: 'My boss and colleagues were very supportive. But I felt self-imposed guilt that my colleagues had to cover for me.'

Ms Tham then took Keon to see a general practitioner, but the fever refused to subside despite medication.

So she took him to hospital, where he was diagnosed with dengue and admitted for three days.

She said: 'The challenging part was that his father was overseas for training, so I had to take him to hospital alone.

'When they told me it was dengue, it sunk in that it could be fatal, and I became more worried and scared.'

That was when she called her husband and mother-in-law to inform them, as she had not wanted to worry them unnecessarily earlier.

Subsequently, she called her husband and sent him photographs of Keon using her mobile phone every day to update him on how the boy was doing.

She had to stay overnight at the hospital all three nights to keep her son company, praying with him and rubbing calamine lotion to soothe the angry red rashes that had started surfacing on his skin.

'He would wake up in the night, crying. I felt so helpless. He was so sick, but all I could do was to apply calamine lotion,' she recalled.

During the day, she had to make two trips home - in the afternoon and the evening - to check on her younger son, Kyler, whom her mother-in-law and her domestic helper were looking after.

It was lucky she could lean on them for support, she said.

The days passed by in a blur. She said: 'I was just too busy and tired to think.'

But every now and then, in the rare moments when she was not comforting Keon or running around from one place to another, anxieties about her unfinished work would pop into her mind.

She would then send text messages to ask her colleagues to make sure that certain aspects of the work were taken care of, and to check if everything was fine.

Just after Keon's discharge from hospital, when Ms Tham should have been able to set her mind at ease, she received another scare.

Kyler started running a fever too, and she had to take him to see a paediatrician.

Fortunately, it turned out to be a false alarm. He did not contract dengue or anything serious.

Ms Tham returned to work soon after, but she made Keon stay at home for two weeks after his discharge, to make sure that he was fully recovered.

And she would call home every day to check that he was fine.

Till today, she remains vigilant against the mosquito-borne disease.

When they moved to their new home in Bishan about five months ago, she made sure that she did not keep plants because she did not want to run the risk of the flowerpot plates collecting stagnant water and breeding mosquitoes.

She said: 'When Keon had dengue, I didn't get enough sleep and there was a lot of unwanted stress. Now my greatest fear is for him to get it again, because it will be more serious.'

This is the first of a three-part series on dengue-fever prevention, brought to you by The National Environment Agency.

This article was first published in The Sunday Times on Feb 8, 2009.